The present invention relates to a high-frequency discharge pumping laser device for producing a high-power laser beam for cutting workpieces of metal, or the like, and more particularly to a high-frequency discharge pumping laser device capable of stable high-frequency discharge pumping.
High-frequency discharge pumping axial-flow CO.sub.2 lasers are finding wide use because of their advantages of high-power output and stable oscillation.
A conventional axial-flow-type high-frequency discharge pumping laser device is illustrated in FIG. 9 of the accompanying drawings. The illustrated laser device includes a discharge tube 1 having four tube segments. However, the discharge tube 1 may have any desired number of tube segments dependent on the output to be produced. A total reflection mirror 2 and an output coupling mirror 3 are accurately positioned at the ends of the discharge tube 1. Denoted at 4 is an outgoing laser beam. The segments of the discharge tube 1 have gas inlet and outlet ports connected to a single roots blower 7. Cooling units 5, 6 serve to cool a laser gas heated by the discharge and the roots blower 7. The laser gas flows in the discharge tube 1 and gas delivery tubes in the directions of the arrows. Electrodes 8a, 8b.about.11a, 11b are connected to respective high-frequency power supplies 12, 13, 14, 15. The gas flows in the discharge tube 1 at the speed of about 100 m/second. An electric discharge is produced in the discharge tube 1 by a high-frequency voltage applied by the high-frequency power supplies 12.about.15 to generate laser oscillation.
The circuit arrangement of one discharge tube segment of the conventional high-frequency discharge pumping laser device is shown in FIG. 10. Denoted at 12 is a high-frequency power supply, and 16 a matching circuit for gaining impedance matching between the high-frequency power supply 12 and the discharge tube 1. The output terminals of the high-frequency power supply 12 are coupled to the electrodes 8a, 8b of the discharge tube 1 through the matching circuit 16, the electrode 8b being grounded.
With such a high-frequency discharge pumping laser device, however, the laser output varies in cyclic periods of about several Hz. Such a laser output fluctuation is illustrated in FIG. 11, with the horizontal axis indicating time and the vertical axis the laser output. As shown in FIG. 11, a laser output fluctuation having the magnitude of about 40 W is produced for a laser output of about 800 W.